> We pretty much know the _theory_ is not correct, just by virtue of> depending on non-architected behaviour. The only thing -ac can do is> test whether it works in practice. Which is a totally different thing.

Yep

> Especially on x86 chips.

Well so far I've found one laptop that eats %cr2 on APM calls, and we havesome mystery cases. Peter's suggestion of using %fs or %gs looks morepromising at the moment